1. Field of the Invention
The invention relates generally to circuit interrupters and, more particularly, to contact arm assemblies for electrical switching apparatus, such as circuit breakers. The invention also relates to crossbar assemblies having a movable contact arm assembly. The invention further relates to electrical switching apparatus having a crossbar assembly and a movable contact arm assembly.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, and other fault conditions. Typically, circuit breakers include a spring powered operating mechanism which opens electrical contacts to interrupt the current through the conductors of an electrical system in response to abnormal conditions.
The electrical contacts generally comprise one or more movable contacts and one or more corresponding stationary contacts. Each pair of separable contacts is electrically connected, in series, between corresponding line and load terminals which are typically positioned at opposite ends of the circuit breaker. More specifically, each movable contact is disposed at or about a first end of a corresponding movable contact arm, which is part of a movable contact assembly. The movable contact arm is pivotably coupled, at or about its second end, to a crossbar of the operating mechanism. A suitable shunt (e.g., without limitation, flexible conductor) electrically connects the movable contact assembly to a load conductor, for example, by way of a clinch joint. The operating mechanism controls the movable contact arm to pivot the movable contact into and out of electrical contact with the corresponding stationary contact. The crossbar carries the movable contact arms for all of the poles of the circuit breaker, and allows for simultaneous opening and closing of the contacts in all of the poles.
Contact pressure between the stationary and movable contacts is typically achieved through the use of compression springs which can commonly attract or be damaged by heat and molten debris produced when each pair of separable contacts is separated and a resulting arc is formed.
As such, there exists a need for improved movable contact arm assemblies and crossbar assemblies for use in electrical switching apparatus.